Recent Advances in Activatable ¹⁹F Magnetic Resonance Imaging Nano‐Probes for the Detection of Biomarkers

Abstract

Adapting MRI to the field of molecular imaging is a challenge that continues to attract considerable attention. The detection of a given biomolecular analyte requires the availability of a molecular probe that is able to respond with a sufficient signal gap in order to overcome the low sensitivity of MRI. To this end, 19F MRI has yielded promising results due to its negligible endogenous background signals. Several small molecular probes have been reported; however, the low sensitivity of 19F MRI render the detection of biomarkers in vivo difficult, in view of their sub‐nanomolar concentration on site. Researchers have thus directed their attention toward larger chemical objects containing large numbers of 19F nuclei as smart platforms that allow a stimuli‐induced response. This article discusses the recent advances and future directions in the design of nano‐probes that respond to chemical or physical stimuli recognized as biomarkers for life and disease.

Dual Nanoparticle Conjugates for Highly Sensitive and Versatile Sensing Using 19F Magnetic Resonance Imaging

“…Of particular interest for molecular imaging are “turn‐on” sensors, in which an imaging probe's signal is quenched until interaction with a specific analyte turns on 19 F signal [30] . These probes are more analyte‐specific than a targeted probe, which gives a signal whether bound to the target or not [31,32] .…”

Vision for Ratiometric Nanoprobes: In Vivo Noninvasive Visualization and Readout of Physiological Hallmarks

“…Being obsessed with improving the accuracy of measurements and reliability of the obtained data has always been the primary driving force for medical scientists to address the shortcomings of the existing techniques. Therefore, to reduce the background signals arising from the agent molecules that nonspecifically reside in healthy tissues, activatable nanoprobes have been suggested. − In contrast to the “always on” nanoprobes, the activatable nanoagents are in their “off” mode while nonspecifically captured outside of the microenvironment of interest. Conversly, upon reaching the microenvironment of the target tissue, they would be turned “on”, begining to perform the function of interest .…”

Frontiers in19F-MR imaging: nanofluorides and19F-CEST as novel extensions to the19F-MRI toolbox

“…The growth of fluorinated molecular probes and their applications in 19 F-MRI continues and many of the developments are beyond the scope of this Feature Article and can be found in other reviews. [35][36][37][38][39] Interestingly, although there are diverse types of probes, the vast majority (if not all) of the used 19 F-probes developed and used are based on organofluorines with a centered carbon-fluorine bond, with no demonstration of the inorganic fluoride-based formulations used for 19 F-MRI. In addition, the MRI signals of these organofluorine formulations rely on the ability to directly detect their well-defined 19 F-MR readout at a specific resonance frequency.…”